TiO2 BASED SCRUBBING GRANULES, AND METHODS OF MAKING AND USING SUCH TiO2 BASED SCRUBBING GRANULES

ABSTRACT

TiO 2  based scrubbing granules, and methods of making and using such TiO 2  based scrubbing granules are described. TiO 2 -based scrubbing granules include granulated TiO 2  and about 0.5% to about 20% dry weight inorganic salt binder. Other TiO 2  based scrubbing granules include unsintered granulated TiO 2  and about 0.5% to about 20% dry weight inorganic salt binder. Inorganic salt binder include sodium aluminate. Methods of making TiO 2  based scrubbing granules include i) combining TiO 2  particles with inorganic salt binder to form TiO 2 -binder mixture comprising from about 0.5% to about 20% dry weight binder; ii) granulating the TiO 2 -binder mixture; and drying the granulated TiO 2 -binder mixture to form TiO 2 -based scrubbing granules. Methods of using such TiO 2 -based scrubbing granules include introducing TiO 2 -based scrubbing granules to remove adherent deposits on an inner surface of a reactor or heat exchanger during processes of forming TiO 2  particles and finishing the formed TiO 2  particles into finished pigment products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No.13/871,278, filed Apr. 26, 2013, which claims priority to provisionalapplication 61/639,624 filed Apr. 27, 2012 titled METHOD OF PRODUCINGTiO₂ SCRUBS AND THEIR USE IN TiO₂ MANUFACTURING PROCESSES.

BACKGROUND

Field of the presently disclosed and/or claimed inventive concept(s).

This invention includes embodiments relating to titanium dioxide (TiO₂)based scrubbing granules, and methods of making and using such TiO₂scrubbing granules. Particularly, the invention includes embodimentsrelating to TiO₂ based scrubbing granules with sodium aluminate binderand various methods of using such TiO₂ based scrubbing granules duringTiO₂ production; and embodiments relating to unsintered TiO₂ basedscrubbing granules with inorganic metal binder and various methods ofusing such TiO₂ based scrubbing granules during TiO₂ production

Background of the presently disclosed and/or claimed inventiveconcept(s).

Generally, TiO₂ particles are produced by a chloride or a sulfateprocess. In the chloride process, titanium tetrachloride (TiCl₄)undergoes vapor phase oxidation to form TiO₂ particles as part of a hotgaseous suspension. The hot TiO₂ particles, along with other gaseousby-products in the hot gaseous suspension, are passed from a reactor toa heat exchanger. The hot gaseous suspensions are cooled by contact withthe inner surface walls of the heat exchanger which have temperaturesless than that of the hot gaseous suspension. As the hot TiO₂ particlesare cooled, the TiO₂ particles may deposit on the inner walls of theheat exchanger or reactor and form adherent layer deposits. The adherentlayer deposits lower heat transfer efficiency through the inner walls ofthe heat exchanger and thus reduce cooling efficiencies. Suchinefficiencies affect the quality of the formed TiO₂ particles and theefficiency of the downstream finishing and surface treatment steps.

In attempts to remove adherent layers, “scrubs” such as sodium chloride(NaCl), silica sand, calcined TiO₂ particles, sintered TiO₂ particleshave been added to the hot TiO₂ pigment particles flowing through thereactor and heat exchanger. For example, NaCl scrubs such as U.S. Pat.No. 3,511,308 increase viscosity of TiO₂ slurry, thereby lowering thethroughput rate in the finishing step. Silica sand scrubs introducecontaminants into the process and may also increase reactor wear anddowntime of the process equipment, e.g., the reactor, the heatexchanger, etc.

U.S. Pat. No. 5,266,108 discloses calcined TiO₂ scrubs typicallyprepared by heating the TiO₂ particles to a maximum temperature ofapproximately 1000° C. Unfortunately, such high temperatures decreasethe surface area of most known TiO₂ scrubs and makes size of scrubsdifficult to control. Calcined or sintered TiO₂ scrubs also have one ormore of the following disadvantages. Calcined or sintered TiO₂ scrubscontaminate the finished TiO₂ pigments, thus requiring additionalprocesses. Calcined or sintered TiO₂ scrubs are difficult to reduce topigmentary size; and calcined or sintered TiO₂ scrubs can affect thedispersion and/or effectiveness of TiO₂ finishing processes.

Thus, a need still exists for improved scrubbing mediums, and method ofmaking and using such improved scrubbing mediums.

BRIEF SUMMARY

Embodiments of the present invention meet these and other needs byproviding TiO₂-based scrubbing granules, and methods of making and usingsuch TiO₂-based scrubbing granules.

Accordingly, one aspect of the invention provides TiO₂-based scrubbinggranules. The TiO₂-based scrubbing granules include granulated TiO₂ andabout 0.5% to about 20% dry weight sodium aluminate binder.

A second aspect of the invention provides TiO₂-based scrubbing granules.The TiO₂-based scrubbing granules include granulated TiO₂ and about 0.5%to about 20% dry weight binder. The binder is selected from a groupconsisting of sodium aluminate, sodium sulfate, sodium phosphate, sodiumsilicate, sodium chloride, sodium hexametaphosphate, and aluminumsulfate, and combinations thereof.

A third aspect of the invention provides TiO₂-based scrubbing granules.The TiO₂-based scrubbing granules include granulated TiO₂ and about 0.5%to about 20% dry weight binder and wherein the TiO₂-based scrubbinggranules are unsintered.

A fourth aspect of the invention provides a method of making TiO₂-basedscrubbing granules. The method includes: i) combining TiO₂ particleswith sodium aluminate binder to form a TiO₂-binder mixture comprisingfrom about 0.5% to about 20% dry weight binder; ii) granulating theTiO₂-binder mixture; and iii) drying the granulated TiO₂-binder mixtureto form TiO₂-based scrubbing granules.

A fifth aspect of the invention provides a method of making TiO₂-basedscrubbing granules. The method includes: i) combining TiO₂ particleswith binder to form a TiO₂-binder mixture comprising from about 0.5% toabout 20% dry weight binder; ii) granulating the TiO₂-binder mixture;and iii) drying the granulated TiO₂-binder mixture to form TiO₂-basedscrubbing granules. The binder is selected from a group consisting ofsodium aluminate, sodium sulfate, sodium phosphate, sodium silicate,sodium chloride, sodium hexametaphosphate.

A sixth aspect of the invention provides a method of making TiO₂-basedscrubbing granules. The method includes: i) combining TiO₂ particleswith a binder to form a TiO₂-binder mixture; ii) granulating theTiO₂-binder mixture; and iii) drying the granulated TiO₂-binder mixtureto form TiO₂-based scrubbing granules without sintering the TiO₂-basedscrubbing granules. The binder comprises from about 0.5% to about 20% bydry weight of the TiO₂-based scrubbing granules.

A seventh aspect of the invention provides a method of using TiO₂-basedscrubbing granules. The method includes:

-   -   i. introducing TiCl₄ into a TiO₂ reaction zone of a reactor to        form TiO₂ particles;    -   ii. introducing TiO₂-based scrubbing granules into the reactor        or a heat exchanger, thereby resulting in a TiO₂ product stream        comprising the TiO₂-based scrubbing granules and formed TiO₂        particles; and    -   iii. cooling the TiO₂ product stream via the heat exchanger,        wherein the TiO₂-based scrubbing granules in the TiO₂ product        stream removes deposits on an inner surface of the heat        exchanger as the TiO₂ product stream comprising the TiO₂-based        scrubbing granules passes through the heat exchanger. The        TiO₂-based scrubbing granules include granulated TiO₂ and about        0.5% to about 20% dry weight sodium aluminate binder.

An eighth aspect of the invention provides a method of using TiO₂-basedscrubbing granules. The method includes:

i. introducing TiCl₄ into a TiO₂ reaction zone of a reactor to form TiO₂particles;

ii. introducing Ti0₂-based scrubbing granules into the reactor or a heatexchanger, thereby resulting in a TiO₂ product stream comprising theTi0₂-based scrubbing granules and formed TiO₂ particles; and

iii. cooling the TiO₂ product stream via a heat exchanger, wherein theTiO₂-based scrubbing granules in the TiO₂ product stream removesdeposits on an inner surface of the heat exchanger as the TiO₂ productstream comprising the TiO₂-based scrubbing granules passes through theheat exchanger. The TiO₂-based scrubbing granules include granulatedTiO₂ particles and about 0.5% to about 20% dry weight binder. The binderis selected from a group consisting of sodium aluminate, sodium sulfate,sodium phosphate, sodium silicate, sodium chloride, sodiumhexametaphosphate, and aluminum sulfate, and combinations thereof.

A ninth aspect of the invention provides a method making TiO₂ particles.The method includes:

i. introducing TiCl₄ into a TiO₂ reaction zone of a reactor to form TiO₂particles;

ii. introducing unsintered TiO₂-based scrubbing granules into thereactor or a heat exchanger, thereby resulting in a TiO₂ product streamcomprising the TiO₂-based scrubbing granules and formed TiO₂ particles;and

iii. cooling the TiO₂ product stream via a heat exchanger, wherein theTiO₂-based scrubbing granules in the TiO₂ product stream removesdeposits on an inner surface of the heat exchanger as the TiO₂ productstream comprising the TiO₂-based scrubbing granules passes through theheat exchanger. The unsintered TiO₂-based scrubbing granules includegranulated and about 0.5% to about 20% dry weight binder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a conventional method of making TiO₂-basedscrubbing granules;

FIG. 2 is a flow chart of a method of making TiO₂-based scrubbinggranules in accordance with an embodiment of the invention;

FIG. 3 is a flow chart of a method of using TiO₂-based scrubbinggranules in accordance with an embodiment of the invention; and

FIG. 4 compares crush strengths of comparative examples calcined TiO₂scrubs A and B and TiO₂ bases scrub granules with NaCl binder inaccordance with an embodiment of the invention;

FIG. 5 compares crush strengths of the same comparative examplescalcined TiO₂ scrubs A and B with TiO₂ based scrub granules with sodiumaluminate as binder without recycle in accordance with an embodiment ofthe invention;

FIG. 6 compares crush strengths of the same comparative examplescalcined TiO₂ scrubs A and B with TiO₂ based scrub granules with sodiumaluminate as binder with multiple recycle in accordance with anembodiment of the invention;

FIG. 7 compares crush strengths of TiO₂ based scrub granules with sodiumaluminate binder compressed respectively under 13.8 barg, 34.5 barg, and69 barg roll pressures in accordance with embodiments of the invention;

FIG. 8 compares crush strengths of TiO₂ based scrub granules with sodiumaluminate binder compressed under 13.8 barg and dried at respectivetemperature conditions in accordance with embodiments of the invention;

FIG. 9 compares crush strengths of TiO₂ based scrub granules with sodiumaluminate binder compressed under 34.5 barg and dried at respectivetemperature conditions in accordance with embodiments of the invention;

FIG. 10 compares crush strengths of TiO₂ based scrub granules withsodium aluminate binder compressed under 69 barg dried at respectivetemperature conditions in accordance with embodiments of the invention;

FIG. 11 is a boxplot comparison of crush strengths of same comparativeexamples calcined TiO₂ scrubs A and B versus TiO₂ based scrubbinggranules with sodium silicate binder, not pressure rolled and dried at100° C. overnight in accordance with embodiments of the invention; and

FIG. 12 is a boxplot comparison of crush strengths of same comparativeexamples calcined TiO₂ scrubs A and B versus TiO₂ based scrubbinggranules with sodium aluminate binder, not pressure rolled and dried at100° C. overnight in accordance with an embodiment of the invention

DETAILED DESCRIPTION

In the following description, it is understood that terms such as “top,”“bottom,” “outward,” “inward,” and the like are words of convenience andare not to be construed as limiting terms. Reference will now be made indetail to exemplary embodiments of the invention, which are illustratedin the accompanying figures and examples. Referring to the drawings ingeneral, it will be understood that the illustrations are for describinga particular embodiment of the invention and are not intended to limitthe invention thereto.

Whenever a particular embodiment of the invention is said to comprise orconsist of at least one element of a group and combinations thereof, itis understood that the embodiment may comprise or consist of any of theelements of the group, individually or in combination with any of theother elements of that group. Furthermore, when any variable occurs morethan one time in any constituent or in formula, its definition on eachoccurrence is independent of its definition at every other occurrence.Also, combinations of substituents and/or variables are permissible onlyif such combinations result in stable compounds.

Definitions

The term calcining refers to the heating up of solids to a hightemperature, but below the incipient fusion or melting point temperatureof the solids. Calcination can result in thermal transition, solidsphase transition, and/or removal of volatile fraction(s) from thesolids. The volatile fraction(s) that is removed is bound with thesolids, and exclude surface volatiles, such as surface water or surfacemoisture. The chemical composition of the product is typically differentfrom that of the reactant. One example of calcination includes thethermal decomposition of limestone via the following reaction:

CaCO₃(solids)+Heat→CaO(solids)+CO₂(gas)

The term sintering refers to the “welding together” and growth ofcontact area between solid particles at temperatures near the meltingpoint of the solids. The solids are heated up to their incipient fusiontemperature (or eutectic point temperature if the solids contain morethan one species of compounds). In this heating process, there is agradual closing of the voids between the particles and densificationtypically occurs. The solid particles stick together due to partialmelting, and form a solid porous mass. Chemical reaction is not takingplace, and the chemical composition of the product(s) is substantiallythe same as the reactant. Examples of sintering include eutectic phasediagrams published in the literature.

Free flowing solids refers to solids capable of flowing out ofcontainers or bins without the aid of flow enhancers, such as binvibrators, bin inserts, or special flow-enhancing liners on the binwall. Free flowing solids also refers to the flow of material from thebin, sticky solids and dry powders that tend to adhere strongly to thesurface of bins resulting in poor control of material flow. Whereas,with granular solids that do not stick to the walls, the flow isconsistent, controlled and hence, called as free flowing.

TIO₂-Based Scrubbing Granules Embodiment 1

An embodiment of the invention includes TiO₂-based scrubbing granules.The TiO₂-based scrubbing granules include granulated TiO₂ and about 0.5%to about 20% dry weight sodium aluminate binder. In another embodiment,the TiO₂-based scrubbing granules further include one or more inorganicsalts. Non-limiting examples of inorganic metal salts include sodiumaluminate, sodium sulfate, sodium phosphate, sodium silicate, sodiumchloride, sodium hexametaphosphate, aluminum sulfate, eitherindividually or in combinations of two or more thereof.

In a particular embodiment, the TiO₂-based scrubbing granules aredispersible in finished TiO₂ pigment during a process of making suchfinished TiO₂ pigment. In yet another embodiment, the TiO₂-basedscrubbing granules are free flowing. An advantage of free flowingTiO₂-based scrubbing granules includes ease of introducing TiO₂-basedscrubbing granules to a location or place such a reactor or heatexchanger.

In an embodiment, the TiO₂-based scrubbing granules are unsintered. Inanother embodiment, the TiO₂-based scrubbing granules are uncalcined. Anembodiment includes TiO₂ based scrubbing granules having an average sizein a range of from about 1 mm to about 25 mm. An embodiment includesTiO₂ based scrubbing granules having a bulk density in a range of fromabout 800 to about 1800 kg/m³.

It should be appreciated that embodiments of the invention includepre-determined and preselected choice of mean size, size distribution,and hardness to provide adequate scrubbing action tailored for specificprocesses and methodologies. Embodiments of the invention includevarying non-limiting parameters such as drying conditions, type ofbinders, amount of binder, the type of pressure rolls, and amount ofpressure applied, either individually and or in combination of two ormore thereof as discussed below.

Embodiment 2

In an embodiment of the invention, TiO₂-based scrubbing granules includegranulated TiO₂ and about 0.5% to about 20% dry weight binder. Thebinder includes one or more inorganic salts such as but not limited tosodium aluminate, sodium sulfate, sodium phosphate, sodium silicate,sodium chloride, sodium hexametaphosphate, and aluminum sulfate, eitherindividually or in combinations of two or more thereof. In a particularembodiment, the binder comprises sodium aluminate. In a particularembodiment, inorganic metal salt includes substantially sodiumaluminate. Similar to as described above, in a particular embodiment,the TiO₂-based scrubbing granules are dispersible in finished TiO₂pigment during a process of making such finished TiO₂ pigment. In yetanother embodiment, the TiO₂-based scrubbing granules are free flowing.

In an embodiment, the TiO₂-based scrubbing granules are unsintered. Anembodiment includes TiO₂ based scrubbing granules having an average sizein a range of from about 1 mm to about 25 mm. An embodiment includesTiO₂ based scrubbing granules having a bulk density in a range of fromabout 800 to about 1800 kg/m³.

Embodiment 3

An embodiment of TiO₂-based scrubbing granules include granulated TiO₂and about 0.5% to about 20% dry weight binder and wherein the TiO₂-basedscrubbing granules are unsintered. In an embodiment, the bindercomprises sodium aluminate. In another embodiment, the binder includesone or more inorganic salts such as but not limited to sodium aluminate,sodium sulfate, sodium phosphate, sodium silicate, sodium chloride,sodium hexametaphosphate, and aluminum sulfate, either individually orin combinations of two or more thereof. In a particular embodiment, thebinder comprises substantially sodium aluminate. In a particularembodiment, the binder comprises greater than 90% by weight sodiumaluminate based on total weight of the binder in the TiO₂-basedscrubbing granules.

Similar to as described above, in a particular embodiment, theTiO₂-based scrubbing granules are dispersible in finished TiO₂ pigmentduring a process of making such finished TiO₂ pigment. In yet anotherembodiment, the TiO₂-based scrubbing granules are free flowing. Anembodiment includes TiO₂ based scrubbing granules having an average sizein a range of from about 1 mm to about 25 mm. An embodiment includesTiO₂ based scrubbing granules having a bulk density in a range of fromabout 800 to about 1800 kg/m³.

Method of Making TIO₂-Based Scrubbing Granules

Embodiment of the invention provide methods of making TiO₂-basedscrubbing granules as described above. For illustration and notlimitation, an embodiment of making TiO₂-based scrubbing granules iscompared to conventional methods as depicted in FIG. 1. A conventionalmethod of making TiO₂-based scrubbing granules includes Step 110 iscombining TiO₂ particles with binder to form a TiO₂-binder mixture. Thebinder does not include sodium aluminate as shown in FIG. 1. Step 120 iscompacting, and or granulating and drying the TiO₂-binder mixture. Step130 is sintering or calcining the TiO₂-binder mixture. In someconventional methods, TiO₂-binder mixture is sintered or calcined,either individually or both.

In contrast to conventional FIG. 1, FIG. 2 describes embodiments of theinvention of making TiO₂-based scrubbing granules. FIG. 2 is a flowchart of an embodiment of a method of making TiO₂-based scrubbinggranules; and the method is not limited by the order or frequency of thesteps unless expressly noted.

The method includes Step 210 combining TiO₂ particles with binder toform a TiO₂-binder mixture comprising from about 0.5% to about 20% dryweight binder.

The method is not limited by the shape, size and kind of TiO₂ particles.Non-limiting examples of TiO₂ particles used to make TiO₂ basedscrubbing granules include rutile, anatase, and brookite, eitherindividually or in a combination of two or more thereof. In anembodiment, the TiO₂ particles include rutile phase or anatase phase,either individually or in a combination of two or more thereof.Furthermore, the TiO₂ particles used to make TiO₂ based scrubbinggranules may be produced from the chloride or sulfate process, eitherindividually or in combination.

In an embodiment, TiO₂ particles are pigmentary sized particles havingan average size greater than 0.20 micron. Furthermore, such TiO₂ pigmentparticles may be in the form of a finished or intermediate product,either individually or in combinations.

Non-limiting embodiments of binders include as described above. Aparticular embodiment of making TiO₂-based scrubbing granules includesproviding sodium aluminate (NaAlO₂) as binder. Using sodium aluminatebinder may have unexpected advantage of TiO₂-based scrubbing granulesdispersing in TiO₂ slurry and minimizing contamination in downstreamprocesses.

In an embodiment, TiO₂ pigment particles are premixed with sodiumaluminate binder and water such that the binder comprises from about0.5% to about 5% NaA1O₂ dry weight of the TiO₂-sodium aluminate bindermixture and moisture content is about 4%-8%. Approximate mixingequipment such as a pin mixer or turbulizer may be used to mix TiO₂ andbinder to make the TiO2-binder mixture. It should be appreciated thatembodiments of the invention include introducing and adjusting the typeand amount of binder to achieve a desired strength.

It should be also appreciated that embodiments of the invention includeintroducing a plurality of binders which differ from each other.Furthermore, the plurality of binders may independently have variouscharacteristics which differ from each other.

Optimally, Step 220 includes compacting the TiO₂-binder mixture underpressure to form the TiO₂-binder mixture into compacted briquettes. Forillustration and not limitation, Ti02-binder mixture may be passedthrough a compacting apparatus such as standard compactors or pressurerolls available in the market

Embodiments of the invention are not limited by how the TiO₂-bindermixture is compacted or by the form, size or shape of the compactedbriquettes. The compacted briquettes can be formed by any suitablemethod. An embodiment includes subjecting TiO₂-binder mixture tosufficient pressure to compact. The TiO₂-binder mixture can be compactedby pressure by any suitable means such as, but not limited to, pressurerolls and presses. A specific embodiment includes counter-rotatingpressure rolls. If desired, the pressure rolls can have depressions onthe surface of the rolls to facilitate compaction. Non-limiting examplesof the form of compacted briquettes include sticks, almonds, bricks,blocks, etc. either individually or in a combination of two or moreforms. Furthermore, properties of each compacted briquettes are alsoindependent of other compacted briquettes. For example, the size orshape of the compacted briquettes may have varying dimensions of depth,width, length and may independently vary from embodiment to embodiment.

The compacted briquettes can be used as is, if the particle size of thecompacted briquettes is as desired. If the size of the compacted TiO₂binder briquettes is too large, optimally, Step 230 includes breakingthe compacted TiO₂ binder briquettes into TiO₂ binder granules.

Compacted TiO₂ binder briquettes can be broken into smaller size byflake breaker or similar equipment to form TiO₂ binder granules. In anembodiment, the compacted briquettes are broken into TiO₂-bindergranules having average size in a range of from about 1 mm to about 25mm. It should be appreciated that the method includes repeating Step 220compacting the TiO₂-binder mixture into compacted briquettes and Step230 breaking the compacted TiO₂ into TiO₂-binder granules as desired.

Step 240 optimally includes screening the TiO₂-binder granules. The TiO₂binder-granules may be screened based on one or more desiredspecifications such as size specification and reprocessed. For example,TiO₂-binder granules may be selected by an average size in a range offrom about 1 mm to about 25 mm. Step 242 optionally includes recyclingthe TiO₂ binder granules. Oversized TiO₂ granules such as about >25 mmin size may be passed through milling equipment and undersized granulessuch as about <1 mm may be recycled to a compaction unit to recompactinto compacted briquettes. Upon screening, TiO₂-binder granules ofdesired size range from about 1 mm to about 25 mm are collected andpassed on to be part of the TiO₂ based scrubbing granules.

Step 260 includes drying the TiO₂ binder granules to less than 1% watercontent to form TiO₂ based scrubbing granules. In a particularembodiment, Step 260 includes drying the TiO₂ binder granules that havebeen screened for a desired specification such as size to less than 1%water content to form TiO₂ based scrubbing granules. Any suitable dryingunit may be used to dry the TiO₂ binder granules and invention is notrestricted by how the TiO₂ binder granules are dried. In an embodiment,TiO₂ binder granules are dried to achieve <1% moisture thereby improvingthe strength of the TiO₂ granules. For example the TiO₂-binder mixturemay be dried by to heating at a temperature in a range of from about 90°C. to about 700° C. In an embodiment, drying temperature may be in arange, such as but not limited to from about 90° C. to about 200° C.Additionally, the temperature may be varied and/or selected in a rangeor value to achieve a desired strength.

Method of making TiO₂-based scrubbing granules optionally, includes Step250 introducing at least some source of nucleating agent to theTiO₂-binder mixture before step 260 drying the TiO₂-binder mixture intoTiO₂ based scrubbing granules. An embodiment includes introducingnucleating agents from 1A metals of the periodic table, eitherindividually or in a combination of two or more thereof. Example ofgroup 1A metals include salts and halides of cesium, either individuallyor combinations of two or more thereof. The method is not limited by thesequential order or frequency of the steps unless expressly as shown inFIG. 2. An embodiment includes Step 250 introducing nucleating agentsimultaneously with step 210 or 220. Another embodiment includes Step260 introducing nucleating agent sequentially before or after step 220compacting the TiO₂-binder mixture. An embodiment includes Step 250introducing nucleating agent before step 220 compacting the TiO₂-bindermixture. It should also be appreciated that embodiments of the inventioninclude introducing a plurality of nucleating agents which differ fromeach other. Furthermore, the plurality of nucleating agents mayindependently have various characteristics. A particular embodimentincludes introducing a plurality of nucleating agents simultaneously orsequentially before Step 260 drying.

Embodiment 1

As shown in FIG. 2, a particular embodiment of making TiO₂-basedscrubbing granules includes: i) combining TiO₂ particles with sodiumaluminate binder to form a TiO₂-binder mixture comprising from about0.5% to about 20% dry weight binder; ii) granulating the TiO₂-bindermixture; and iii) drying the granulated TiO₂-binder mixture to formTiO₂-based scrubbing granules.

Embodiment 2

As shown in FIG. 2, another particular embodiment of making TiO₂-basedscrubbing granules includes: i) combining TiO₂ particles with binder toform a TiO₂-binder mixture comprising from about 0.5% to about 20% dryweight binder; ii) granulating the TiO₂-binder mixture; and iii) dryingthe granulated TiO₂-binder mixture to form TiO₂-based scrubbinggranules. The binder is selected from a group consisting of sodiumaluminate, sodium sulfate, sodium phosphate, sodium silicate, sodiumchloride, sodium hexametaphosphate.

Embodiment 3

In contrast to conventional method as shown in FIG. 1, embodiments ofthe invention include making TiO₂-based scrubbing granules withoutsintering or calcining the TiO₂-based scrubbing granules. A particularembodiment includes: i) combining TiO₂ particles with a binder to form aTiO₂-binder mixture; ii) granulating the TiO₂-binder mixture; and iii)drying the granulated TiO₂-binder mixture to form TiO₂-based scrubbinggranules without sintering the TiO₂-based scrubbing granules as shown inFIG. 2. The binder comprises of from about 0.5% to about 20% by dryweight of the TiO₂-based scrubbing granules.

Similar to the embodiments of TiO₂-based scrubbing granules describedabove, in an embodiment, the the bulk density of the unsintered TiO₂scrubbing granules formed is in the range of from about 800 to about1800 kg/m³. In a particular embodiment, the unsintered TiO₂-basedscrubbing granules are dispersible in TiO₂ slurry during a process ofmaking finished TiO₂ pigment. In another embodiment, the unsinteredTiO₂-based scrubbing granules are mixed with finished TiO₂ pigmentduring a process of making such finished TiO₂ pigment. In yet anotherembodiment, the unsintered TiO₂-based scrubbing granules are freeflowing.

Method of Using TIO₂-Based Scrubbing Granules

Embodiments of the invention also include methods of using the TiO₂based scrubbing granules described above such as to remove adherentdeposits and make finished TiO₂ pigment. FIG. 3 is a flow chart of anembodiment of a method of removing adherent deposits and making finishedTiO₂ pigment using one or more of the above described TiO₂-basedscrubbing granules. Step 310 includes introducing TiCl₄ into a TiO₂reaction zone of a reactor to form TiO₂ particles. It is understood toone of ordinary skill in the art that TiCl₄ is oxidized in the reactionzone of the reactor to form TiO₂ particles. Step 320 includesintroducing TiO₂-based scrubbing granules into the reactor or a heatexchanger resulting in a TiO₂ product stream comprising the TiO₂-basedscrubbing granules and formed TiO₂ particles.

The method is not limited by the order or frequency of the steps unlessexpressly noted. As shown in FIG. 3, the method is not limited bysequential order or frequency of Step 310 and 320. An embodiment of themethod includes introducing TiCl₄ and TiO₂-based scrubbing granules intothe reactor simultaneously. Another embodiment includes introducingTiCl₄ and TiO₂-based scrubbing granules into the reactor sequentially.

Embodiments of the invention include Step 320 introducing TiO₂-basedscrubbing granules into the reactor before, during or after Step 310introducing TiCl₄ into a TiO₂ reaction zone. In a particular embodiment,a plurality of TiO₂ based scrubbing granules which differ from eachother are introduced into the reactor before, or after introducing TiCl₄into the TiO₂ reaction zone.

In a sequential embodiment, the method include Step 320 introducingTiO₂-based scrubbing granules into the reactor before Step 310introducing TiCl₄ into the TiO₂ reaction zone. Another embodimentincludes Step 320 introducing TiO₂-based scrubbing granules into thereactor during Step 310 introducing TiCl₄ into TiO₂ reaction zone.Another embodiment includes Step 320 introducing TiO₂-based scrubbinggranules into the reactor after Step 310 introducing TiCl₄ into the TiO₂reaction zone.

An embodiment includes introducing TiO₂-based scrubbing granules havingabout 0.5% to about 20% dry weight binder; and the binder includessodium aluminate, sodium sulfate, sodium phosphate, sodium silicate,sodium chloride, sodium hexametaphosphate, and aluminum sulfate, eitherindividually or in a combination of two or more thereof. In a particularembodiment, the method includes introducing TiO₂-based scrubbinggranules having about 0.5% to about 20% dry weight sodium aluminatebinder.

It should be appreciated embodiments of the invention include methods ofremoving adherent deposits by introducing embodiments of the TiO₂-basedscrubbing granules described above to one or more locations such as areactor and or a heat exchanger.

In an embodiment, a plurality of TiO₂ based scrubbing granules whichdiffer from each other are introduced into the reactor or heatexchanger. Furthermore, the plurality of TiO₂ based scrubbing granulesmay have various characteristics.

Embodiment 1

An embodiment includes introducing unsintered TiO₂-based scrubbinggranules into the reactor. In an embodiment, the unsintered TiO₂-basedscrubbing granules have from about 0.5% to about 20% dry weight binder;and the binder includes one or more sodium aluminate, sodium sulfate,sodium phosphate, sodium silicate, sodium chloride, sodiumhexametaphosphate, and aluminum sulfate, either individually or in acombination of two or more thereof. In a particular embodiment, theunsintered TiO₂-based scrubbing granules have from about 0.5% to about20% dry weight sodium aluminate binder.

In an embodiment of the invention, the introduced unsintered TiO₂scrubbing granules have an average size in a range from about 1 mm toabout 25 mm. It should be appreciated that embodiments of the inventioninclude pre-determined and preselected choice of size, distribution, andhardness to provide adequate scrubbing action tailored for specificprocess and/or methodology. Embodiments of the invention include varyingnon-limiting parameters such as drying conditions, binder, amount ofbinder, type of pressure rolls, and amount of pressure applied, eitherindividually and or in combination of two or more thereof as discussedbelow.

In one embodiment, the bulk density of the unsintered TiO₂ basedscrubbing granules introduced into the reactor or heat exchanger is in arange of from about 800 to about 1800 kg/m³. In a particular embodiment,the TiO₂ based scrubbing granules are generally free flowing to simplifyintroduction of such TiO₂ based scrubbing granules into reactor and/orthe heat exchanger.

Embodiment 2

In an embodiment of the invention, the introduced TiO₂-based scrubbinggranules include granulated TiO₂ and about 0.5% to about 20% dry weightbinder. The binder includes one or more inorganic salts such as but notlimited to sodium aluminate, sodium sulfate, sodium phosphate, sodiumsilicate, sodium chloride, sodium hexametaphosphate, and aluminumsulfate, either individually or in combinations of two or more thereof.In a particular embodiment, the binder comprises sodium aluminate.

Similar to as described above, in an embodiment, the TiO₂-basedscrubbing granules are unsintered. In another embodiment, the TiO²-basedscrubbing granules further include one or more inorganic salts. Examplesof inorganic metal salt include sodium aluminate, sodium sulfate, sodiumphosphate, sodium silicate, sodium chloride, sodium hexametaphosphate,aluminum sulfate, either individually or in combinations of two or morethereof.

In an embodiment of the invention, the TiO₂-based scrubbing granuleshave an average size in a range of from about 1 mm to about 25 mm. Inone embodiment, the bulk density of the TiO₂-based scrubbing granules isin a range of from about 800 to about 1800 kg/m³. The TiO₂-basedscrubbing granules are generally but without limitation, free flowingwhich facilitates feeding of TiO₂-based scrubbing granules into processequipments such as reactors and heat exchangers.

Step 330 includes cooling the TiO₂ product stream via a heat exchanger.The TiO₂-based scrubbing granules in the TiO₂ product stream removesdeposits from an inner wall of the heat exchanger as the TiO₂ productstream comprising the TiO₂-based scrubbing granules passes through theheat exchanger. The TiO₂ based scrubbing granules remove deposits orresidues within apparatus such as reactors and heat exchangers used inthe production of TiO₂ pigment particles via a chloride process asdescribed here. In addition to removing deposits, TiO₂ based scrubbinggranules also increase and/or maintaining heat transfer efficienciesthrough the inner walls of the heat exchanger.

Embodiments of the invention include adjusting and varying the amount ofTiO₂ based scrubbing granules that is introduced (Step 320) to removeadherent layer deposits depending upon particular processing conditions,procedures, functional limitations, etc. within the scope and skills ofone of ordinary skill in the art given. An embodiment includesintroducing one or more combinations of TiO₂ based scrubbing granuleswith selected characteristics to provide a predetermined scrubbingefficiency. Furthermore, the introduced TiO₂-based scrubbing granuleswith the selected characteristics may be altered or changed in responseto a change in the predetermined scrubbing efficiency. An embodimentincludes increasing or decreasing the amount of introduced TiO₂ basedscrubbing granules in response to one or more change in a scrubbingefficiency, either individually or combinations thereof. For example, anembodiment includes decreasing the amount of introduced TiO₂ basedscrubbing granules as accumulated adherent deposits on the inner wall ofthe heat exchanger or reactor decrease or vice versa. Amount ofscrubbing granule introduced may also be adjusted based upon thetemperature limit of downstream equipment i.e. filter inlet temperaturescontrols feeding rate of scrubs.

In an embodiments, TiO₂ based scrubbing granules are introduced into thereactor and/or heat exchanger in the range from about 0.5 to about 20wt. % based on total TiO₂ particle production rate in the reactor. Inanother embodiments, TiO₂-based scrubbing granules are introduced in arange from about 1 to about 10 wt. % based on total TiO₂ particleproduction rate in the reactor, to remove accumulated adherent layersand thereby improves heat transfer efficiency. In yet anotherembodiment, TiO₂ scrubbing granules are introduced in a range from about1 to about 5 wt. %, based on total TiO2 particle production rate in thereactor. In an embodiment, TiO₂ based scrubbing granules are introducedin an amount such that the reaction mass exiting the heat exchanger willbe at a temperature compatible with downstream process equipment such ascyclones, filters, and screw conveyers.

Furthermore, embodiments of the invention optionally include Step 350introducing a nucleating agent, such as from 1A metals of the periodictable, either individually or in a combination of two or more thereof.Non -limiting examples of nucleating agents include salts and halides ofcesium, either individually or in combinations of two or more thereofof. The method is not limited by the order or frequency of the stepsunless expressly noted. As shown in FIG. 3, the method is not limited bysequential order or frequency of Step 350.

Optionally, embodiments include Step 350 introducing nucleating agentbefore, during or after step 320 introducing TiO₂-based scrubbinggranules into the reactor. An embodiment of the method includes Step 350introducing nucleating agent and step 320 introducing TiO₂-basedscrubbing granules into the reactor simultaneously. An embodiment of themethod includes Step 350 introducing nucleating agent and step 320introducing TiO₂-based scrubbing granules into the reactor sequentially.

A sequential embodiment includes Step 350 introducing nucleating agentbefore Step 320 introducing TiO₂-based scrubbing granules into thereactor. Another sequential embodiment includes Step 350 introducingnucleating agent after Step 320 introducing TiO₂-based scrubbinggranules into the TiO₂ reaction zone. It should be appreciated that themethod includes repeating Step 350 as desired, simultaneously orsequentially.

An embodiment includes introducing nucleating agents from 1A metals ofthe periodic table, either individually or in a combination of two ormore thereof. Example of group 1A metals includes salts and halides ofcesium. Salts or halides of cesium may control or reduce the particlesize distribution of the TiO₂ finished product. It should be appreciatedthat one or more group 1A metal nucleating agents can also be usedinstead of, or as a mixture with KCl as nucleating agents.

Step 340 optionally includes recovering the cooled TiO₂ particles andTiO₂-based scrubbing granules from the TiO₂ product stream after havingpassed through the heat exchanger. The recovered cooled TiO₂ particlesand TiO₂-based scrubbing granules may be recovered such as via a bagfilter which separates solid TiO₂ particles from gas. Embodiments of theinvention also include various finishing processes to form the recoveredTiO₂ particles and TiO₂-based scrubbing granules into finished TiO₂pigment.

A finishing process includes Step 360 forming some of the recovered TiO₂particles and TiO₂-based scrubbing granules into finished TiO₂ pigmentvia dry finishing process.

Another finishing process includes Step 370 introducing some of therecovered TiO₂ particles and TiO₂-based scrubbing granules into a slurrytank to form finished TiO₂ pigment via wet finishing process. Unexpectedadvantages of using TiO₂ based scrubbing granules include one or more ofthe following. In an embodiment, the TiO₂-based scrubbing granules aredispersible in the aqueous slurry and disperse into TiO₂ particles suchthat the TiO₂-based scrubbing granules do not need to be removed. TheTiO₂ scrubbing granules are capable of being dispersed within theaqueous slurry without introducing foreign contaminants or oversizedTiO₂. The TiO₂-based scrubbing granules may also be interspersed withinthe finished TiO₂ pigment. Thus, embodiments include finished TiO₂pigment with interdispersed TiO₂-based scrubbing granules.

Furthermore, the TiO₂-based scrubbing granules may be interspersedwithin the finished TiO₂ pigment without affecting the quality of thefinished TiO₂ pigment. As the TiO₂-based scrubbing granules do notsignificantly degrade or change the physical and or chemicalfunctionality of finished TiO₂ pigment, the TiO₂-based scrubbinggranules have the unexpected advantages of not needing to be separatedfrom the finished TiO₂ pigment, not needing to be recycled, and notneeding further processing. An embodiment of the invention includes notseparating TiO₂-based scrubbing granules from the finished TiO₂ pigmentand the finished TiO₂ pigment may be sold and/or used with theTiO₂-based scrubbing granules as a component thereof.

Furthermore, Applicant has also unexpectedly discovered that NaCl orsilica sand scrub may be reduced or replaced with one or moreembodiments of TiO₂ based scrubbing granules of the present inventions.NaCl scrubs increase viscosity of TiO₂ slurry, thereby lowering thethroughput rate in the finishing step. Silica sand scrubs introducecontaminants into the process and may also increase reactor wear anddowntime of the process equipments such as reactors and heat exchangers.An embodiment includes TiO₂ based scrubbing granules substantially freeof NaCl. An embodiment includes TiO₂ based scrubbing granulessubstantially free of silica sand. Unexpected advantages includeimproved throughput rate in the finishing step and increased operatinglife of process equipment the reactor, the heat exchanger, etc.

Another unexpected advantage of embodiments of TiO₂ based scrubbinggranules of the present invention includes minimizing trace metalpick-up by TiO₂ particles. Embodiments of TiO₂ based scrubbing granulesare not as hard as conventional silica sand or sintered TiO₂ as shown inFIG. 1 which tends to abrade the walls of process equipments such asreactors and heat exchangers and result in metal pick affecting thequality of finished TiO₂ product.

EXAMPLES

The following examples illustrate the features of embodiments of theinvention and are not intended to limit the invention thereto.

Experimental Results and Analysis

TiO₂ pigment particles and binder were mixed to form a TiO₂-bindermixture; and TiO₂-binder mixture was compacted to form various types ofTiO₂-based scrubbing granules in studies.

Lab studies were conducted on two compaction processes, pressure rollcompaction using an L-83 compactor from Fitzpatrick Company andcompaction using a lab scale DISPERMAT® from VMA-Getzmann. Binders suchas sodium aluminate (NaAlO₂), sodium silicate (Na₂SiO₃), and sodiumchloride (NaCl) were selected for study. Crush strength tests were usedto qualitatively compare TiO₂-based scrubbing granules in accordancewith embodiments of the invention with comparative calcined TiO₂ scrubsexamples A and B.

Comparative calcined TiO₂ scrubs examples A and B are calcined sulfateTiO₂ scrub materials with different additives and at calcinationtemperature of 970° C. to 1020° C. Such calcined TiO₂ scrub materialswere manufactured by sulfate TiO₂ manufacturing process. Pressurecompaction with the L-83 compactor showed that TiO₂-based scrubbinggranules in accordance with embodiments of the invention exhibitedsimilar or higher strength than comparative examples A and B calcinedTiO₂ scrubs. Lab studies demonstrate that characteristics and quality ofthe TiO₂-based scrubbing granules in accordance with embodiments of theinvention described above may be affected by, for example, the choice ofbinder, binder concentration, roll pressure, pre-mixing of binder andpigment prior to pressure rolling, initial moisture content, dryingtemperature, recycling of fines, either individually or combinationsthereof.

Pressure Compaction

Pressure compaction was performed using a Pilot scale pressure roller(L-83 compactor from The Fitzpatrick Company). In a test procedure, anappropriate amount of binder and TiO₂ particles were premixed to formTiO₂-binder mixture in accordance with embodiments of the inventiondescribed above. TiO₂-binder mixture was placed on a roller mill forabout 45 minutes to achieve uniform mixing of the binder and TiO₂pigment. The TiO₂-binder mixture was then compacted via a pressureroller at 69 barg roll pressure and at 5 rpm roll speed to formcompacted briquettes. The compacted briquettes were then dried in laboven at 100C overnight. The compacted briquettes were dried such that itcontains <1% moisture. The dried compacted briquettes were then sievedand briquettes greater than 3 mm were selected for crush strengthanalysis. Compacted briquettes of 3mm and above were chosen so that aqualitative comparison of crush strength analysis can be done withCristal A and Cristal B calcined scrubs. Results from the screeningexperiments are discussed below.

Sodium Chloride as Binder

FIG. 4 shows the crush strength values for compacted briquettes formedwith respectively 0.5% and 5% NaCl binder compared to the comparativeexample A and B calcined TiO₂ scrubs. An increase in strength of thecompacted briquettes was observed with increase in binder concentrationfrom 0.5% to 5%. However, the average crush strength in both cases waslower than the crush strength of comparative example A calcined TiO₂scrub.

Sodium Aluminate as Binder

FIG. 5 shows the crush strength values compacted briquettes formed withrespectively 1% and 2% sodium aluminate (“SA”) binder compared to thecomparative A and B calcined TiO₂ scrubs. Again, an increase in strengthof the compacted briquettes was observed with increase in binderconcentration.

Effect of Premixing

Binder and TiO₂ pigment particles were premixed in batches using a mixerDISPERMAT™. During mixing, water was added to attain an initial moisturecontent of about 7%. With 2.5% sodium aluminate as binder, the averagecrush strength of compacted briquettes was about three times of thecomparative A calcined TiO₂ scrubs as shown in FIG. 6. The term“compacts” as used herein and in the figures refers to briquettesproduced by pressure rolling. The briquettes are broken down to granulesof required specification. Comparison of FIGS. 5 and 6 shows significantincrease in the crush strength of [compacted briquettes formed bypre-mixing of sodium aluminate (“SA”) binder and TiO₂ pigment prior topressure rolling.

Effect of Roll Pressure and Recycle

The effect of roll pressure and recycling of fines on the quality ofbriquettes that are formed was studied. 2.5% Sodium aluminate binder(based on previous results with higher crush strength) and TiO₂ pigmentparticles were premixed and an initial moisture content of about 7% wasachieved. Effect of roll pressures of 13.8 barg, 34.5 barg, and 69 bargand recycle of fines or briquettes smaller than 3.3 mm were studied.

FIG. 7 shows pressure rolling and recycling significantly affect thequality of briquettes that are formed. Average crush strength ofbriquettes formed at roll pressure of 13.8 barg is higher than at rollpressure of 69 barg with or without recycling. However, crush strengthfor a roll pressure of 34.5 barg is slightly higher than those valuesobtained at 13.8 barg.

Effect of Drying Temperature

The effect of drying temperature on the quality and strength ofcompacted briquettes in accordance with embodiments of the inventiondescribed above were also studied. The compacted briquettes dischargedfrom the pressure roll was dried at 100° C. (overnight), 300° C. (1hour), 500° C. (1 hour) and 700° C. (1 hour). TiO₂-binder mixtureincluded 2.5% sodium aluminate binder premixed with TiO₂ pigment with aninitial moisture content of about 7%. The TiO₂-binder mixture werecompacted into briquettes via pressure roll and respectively dried at100° C. (overnight), 300° C. (1 hour), 500° C. (1 hour) and 700° C. (1hour).

FIGS. 8-10 crush data show that, independent of the compacting rollpressure, an increase in drying temperature increases crush strength ofthe compacted briquettes.

Granulation Studies Using Lab Scale Mixer

In these studies, TiO₂ Spray Dryer Discharge pigment particles, binder,and water were combined. A mixer DISPERMAT™ fitted with a 50 mmhigh-shear impeller, was used for mixing.

In the test procedure, amounts of binder and TiO₂ pigment were placed inthe mixer and mixed at about 300 rpm speed. During mixing, water wasadded to obtain an initial moisture content of about 6% to 8%. Mixingwas continued for about 10-15 minutes or until TiO₂-binder mixturesticking to the mixer was observed. TiO₂-binder granules formed werethen dried in an oven at 100° C. overnight. The dried TiO₂ basedscrubbing granules was then sieved into different mass fractions. TiO₂based scrubbing granules larger than 3 mm in size were taken andanalyzed for crush strength.

Sodium Silicate as Binder

TiO₂-binder mixture with respectively 1%, 2%, and 3% sodium silicatebinder and TiO₂ pigment in accordance with embodiments of the inventionwere mixed as described above. FIG. 11 shows comparison of crushstrength values of TiO₂-based scrubbing granules with respectively 1%,2%, and 3% sodium silicate binder compared to comparative examples A andB calcined TiO₂ scrubs.

Crush strength values of TiO₂-based scrubbing granules with 1%, and 2%sodium silicate binder are similar to comparative example A calcinedTiO₂ scrub, whereas, TiO₂ based scrubbing granules with 3% sodiumsilicate binder have a lower average crush strength value than thecomparative example A calcined TiO₂ scrub, but a higher value thancomparative example B calcined TiO₂ scrub.

Sodium Aluminate as Binder

TiO₂-binder mixture with respectively 1%, 2%, and 3% sodium aluminatebinder and TiO₂ pigment were mixed as described above. FIG. 12 comparesof crush strength values of TiO₂-based scrubbing with respectively 1%,2%, and 3% sodium aluminate binder. Average crush strength values ofTiO₂-based scrubbing granules with 1%, 2% and 3% sodium aluminate binderare higher than comparative examples A and B calcined TiO₂ scrubs.

In general, with all tested binders, the crush strength of thegranulated TiO2-based scrubbing granules increased as binderconcentration increased from about 0.5% to about 3%. TiO₂-basedscrubbing granules formed with sodium aluminate as a binder had highercrush strength values when compared to sodium silicate or sodiumchloride as binders. Also, granulated TiO₂-based scrubbing granules withsodium aluminate showed an increased crush strength as (1) binderconcentration increased from 0.5% to 2.5%, (2) drying temperatureincreased from 100° C. to 700° C., (3) granules or briquettes of lessthan 3.0 mm in size were recycled, and (4) initial moisture content wasincreased from 3% to 7%.

Pilot Scale Studies

Pilot scale studies were performed at a vendor facility to corroboratethe laboratory results described above.

Sodium aluminate was used as the binder for the pilot studies. Twoexperiments with binder levels of 2.5% and 4% sodium aluminate inaccordance with embodiments of the invention described above wereconducted. As in Step 210 FIG. 2, sodium aluminate binder was mixed withTiO₂ spray dryer discharge using a mixer Turbulizer™ (model TCJS-8) toform a TiO2-binder mixture. As in Step 220, the TiO₂-binder mixture wascompacted using a pilot scale MS-75 compaction system at 454 kg/hourfeed rate.

As in Step 230, the compacted briquettes were broken into granules viapassing through a flake breaker; Sweco 60″ screener and a Frewitt™granulator produce TiO₂ binder granules of desired size (e.g., 3.36 mm×1mm or 2 mm×1 mm). As in Step 240 screening, TiO₂ binder granules smallerthan 1 mm were recycled to the feed hopper whereas granules greater than3.36 mm or 2 mm were recycled to the granulator. The TiO₂-based bindergranules meeting the above-noted specifications was collected and driedas in Step 260 to less than 1% moisture by to form TiO₂ based scrubbinggranules. TiO₂-based binder granules were dried passing through a 1 m²fluid bed dryer. The strength of the TiO₂₋based binder granules producedwas tested using an attrition method as described below.

Attrition Test Method:

TiO₂-based binder granules s in accordance with embodiments of theinvention were compared to comparative calcined TiO₂ scrubs examples Aand B using attrition tests.

The attrition test was run by screening TiO₂ based scrubbing granulesusing a Ro-Tap® sieve shaker, fitted with screens the same size as orslightly finer than the desired product, for five minutes typically. Allfines (smaller than 20 mesh) were discarded. Fifty grams of the productlarger than 20 mesh were placed on the 20 m mesh screen with (50) ⅜″steel balls (171.18 g). The Ro-Tap® sieve shaker was run for fiveminutes without tapper. The percentage of fines (<20 mesh) found in thepan as a result of the attrition from the steel balls is the attritionnumber. A lower number indicates harder granules.

The average attrition number of TiO₂ binder granules (undried) and theTiO₂ based scrubbing granule (dried TiO₂ binder granules) at 165° C.were respectively 20% and 1.5% , indicating the desirability of dryingto form harder granules. The average attrition value of Comparativeexample A calcined TiO₂ scrub was 6.7% compared to the 1.5% achievedthrough an embodiment of the present invention; thus, embodiments ofmethods of the invention formed harder granules than the comparativeexample A calcined TiO₂ scrub. The attrition numbers did not changesignificantly (1.3% vs. 1.5% seen in Table 1 below) when the binderlevel was increased from 2.5% to 4%, thereby confirming laboratoryresults described above. Increasing binder levels from 0.5% to 2.5%formed harder TiO₂ based scrubbing granules; but, significant impact wasnot observed when binder level was increased above 2.5%. In addition, at4% binder level, processing issues related to caking in the compactionfeed hopper was observed. The drying temperature in the fluid bed dryerwas varied from about 121° C. to about 165° C.

TABLE 1 Results of pilot study using compactor Test # 1 2 TiO2 Feed Rate(lb/hr) 1,000 1,000 Sodium Aluminate*  2.50%  4.00% MS75 Roll Face StickStick MS75 Roll (psi) 500 500 MS75 Roll (rpm) 3.5 3.5 MS75 screw typeStraight Straight Screw Speed (rpm) 118 100 Product Attrition Fresh29.20% 26.80% Product Attrition Cured  1.30%  1.50%

Laboratory finishing process evaluation was conducted using the TiO₂based scrubbing granule produced through a MS75™ compaction system asdescribed above. As described in FIG. 3, TiO₂-based binder granules wereintroduced into Oxidizer TiO₂ slurry and processed through sand mills,treatment, drying and milling processes as is typically performed toproduce commercially acceptable finished TiO₂ product such as finishedTiO₂ pigment. The effect of TiO₂ based scrubbing granules on finishedTiO₂ pigment was evaluated for performance in a paint application. Table2 is a Laboratory Investigation result of Performance Prototype Samplesprepared in Lab; Micronized at Pilot Plant using air at 290° C. andTiO₂=0.227 kg/min

Unexpected results show that finished TiO₂ pigment with some of the ofTiO₂ based scrubbing granule were substantially identical when comparedto finished product TiONA® 595 that did not include the TiO₂ basedscrubbing granule. Lab finishing process compatibility studies in Table2 with TiONA® 595 oxidizer base mixed with 5% TiO₂ based scrubbinggranules show that there was no difference in the quality of finishedTiO₂ pigment formed when compared to TiONA® 595 without the TiO₂ basedscrubbing granules. Such results indicate that the TiO₂-based bindergranules do not need to be removed from the finished TiO₂ pigment.Furthermore, results indicate that using sodium aluminate binder doesnot appear to introduce contamination and/or impart undesirableproperties into finished TiO₂ pigment.

TABLE 2 Lab Investigation - Effect of TiO₂ - based scrubbing granules onProduct Performance Interior high-gloss Interior high-gloss ExteriorSample Mean/ IEP latex paint Brightness latex paint Gloss Tint baseDescription GSD pH % L Δb 20° 60° % L Δb TiONA 595 ™ 0.280/ 7.3 100 0 55 100.2 −0.1 Oxidizer base + 1.424 5% Scrubs, then sandmilled, surfacetreated, dried in lab TiONA 595 ™ 0.277/ 7.5 100 0.15 4 5 100.2 −0.11Oxidizer base + 1.409 5% Scrubs, then sandmilled, surface treated, driedin lab Baseline - 0.274/ 7.52 100.1 0.05 5 5 100.2 −0.2 TiONA 595 ™1.401 oxidizer base as Note: GSD is Geometric Standard Deviation; IEP isIsoelectric Point

Each of the patents, published patent applications, references andarticles cited herein is hereby expressly incorporated herein byreference in its entirety.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the method and system of thepresent invention without departing from the spirit or scope of theinvention. Thus, it is intended that the presently disclosed and/orclaimed inventive concept(s) includes modifications and variations thatare within the scope of the appended claims and their equivalents.

While the presently disclosed and/or claimed inventive concept(s) hasbeen described in detail in connection with only a limited number ofaspects, it should be understood that the presently disclosed and/orclaimed inventive concept(s) is not limited to such disclosed aspects.Rather, the presently disclosed and/or claimed inventive concept(s) canbe modified to incorporate any number of variations, alterations,substitutions, or equivalent arrangements not heretofore described butwhich are commensurate with the scope of the claims. Additionally, whilevarious embodiments of the presently disclosed and/or claimed inventiveconcept(s) have been described, it is to be understood that aspects ofthe presently disclosed and/or claimed inventive concept(s) may includeonly some of the described embodiments. Accordingly, the presentlydisclosed and/or claimed inventive concept(s) is not to be seen aslimited by the foregoing description but is only limited by the scope ofthe appended claims.

What is claimed is:
 1. A method comprising: i. introducing TiCl₄ into aTiO₂ reaction zone of a reactor to form TiO₂ particles; ii. introducingTiO₂-based scrubbing granules into the reactor or a heat exchanger,thereby resulting in a TiO₂ product stream comprising the TiO₂-basedscrubbing granules and formed TiO₂ particles; wherein the TiO₂ basedscrubbing granules comprise: a. granulated TiO₂; and b. sodium aluminatebinder comprising from about 0.5% to about 20% by dry weight of theTiO₂-based scrubbing granules; and iii. cooling the TiO₂ product streamvia the heat exchanger, wherein the TiO₂-based scrubbing granules in theTiO₂ product stream removes deposits on an inner surface of the heatexchanger as the TiO₂ product stream comprising the TiO₂-based scrubbinggranules passes through the heat exchanger.
 2. The method of claim 1,wherein the introduced TiO₂-based scrubbing granules are unsintered. 3.The method of claim 1, further comprising introducing TiO₂-basedscrubbing granules comprising an inorganic salt selected from the groupconsisting of sodium sulfate, sodium phosphate, sodium silicate, sodiumchloride, sodium hexametaphosphate, aluminum sulfate, and combinationsthereof.
 4. The method of claim 1, further comprising recovering thecooled TiO₂ particles and TiO₂-based scrubbing granules from the heatexchanger.
 5. The method of claim 4, further comprising finishing therecovered TiO₂ particles into finished TiO₂ pigment via a wet finishingprocess.
 6. The method of claim 5, comprising finishing the recoveredTiO₂ particles by introducing the recovered TiO₂ particles and recoveredTiO₂-based scrubbing granules into a slurry tank to form the finishedTiO₂ pigment.
 7. The method of claim 5, further comprising not removingthe TiO₂-based scrubbing granules from the finished TiO₂ pigment.
 8. Themethod of claim 1, further comprising introducing a nucleating agent tothe TiO₂ reaction mixture before, during, or after the TiO₂-basedscrubbing granules are introduced.
 9. The method of claim 8, wherein thenucleating agent comprises a salt or halide of a group IA metal.
 10. Themethod of claim 8, wherein the nucleating agent is selected from thegroup consisting of potassium, cesium, and combinations thereof.
 11. Themethod of claim 8, wherein the nucleating agent is selected from a groupconsisting of KCl, CsCl, and combinations thereof.
 12. The method ofclaim 1, wherein the TiO₂-scrubbing granules are free flowing.
 13. Themethod of claim 1, further comprising altering a selected characteristicof the introduced TiO₂ based scrubbing granules in response to a changein a predetermined scrubbing efficiency.
 14. The method of claim 13,further comprising increasing or decreasing the amount of introducedTiO₂ based scrubbing granules in response to a change in thepredetermined scrubbing efficiency.
 15. The method of claim 1, whereinthe TiO₂-based scrubbing granules are introduced in an amount in rangefrom about 1% to 10% weight percent of the total TiO₂ production rate inthe reactor.